docs: def _delete_instructions(self, instruction, value=None):
          """
          :param instruction: name of instruction to be deleted
          :param value: if specified, delete instruction only when it has this value
                        if instruction is LABEL then value is label name
          """
          if instruction == 'LABEL' and value:
              self._modify_instruction_label(value, None)
              return
          if instruction == 'ENV' and value:
              self._modify_instruction_env(value, None)
              return
  
          lines = self.lines
          deleted = False
          for insn in reversed(self.structure):
              if insn['instruction'] == instruction:
                  if value and insn['value'] != value:
                      continue
                  deleted = True
                  del lines[insn['startline']:insn['endline'] + 1]
          if deleted:
              self.lines = lines